Joan Bakewell: Why can't the Speaker's wife use a bus pass?

The Freedom of Information Act makes nosey parkers of us all. That, plus the activities of the TaxPayers' Alliance, offers us gossip and innuendo to match anything in Heat magazine. What is more, we have a stake in the whole, gorgeous story of the Commons Speaker Michael Martin's expenses. For a start, aren't we ourselves paying for this grotesque charade? And second, don't we identify in some small way with the squirming guilt of the named parties.

For myself, I am very worried about Mrs Mary Martin's shopping. Some £4,000 in taxi fares, so the allegation is, to take her to the supermarket – perhaps many supermarkets, or certainly many visits – simply to fetch the groceries. For me, that is just not enough information. I want more, much more. Did she have a list of what she wanted so she could scoot round the shelves and not keep the taxi waiting too long? Did she go for shiny, packaged vegetables or the scruffy organic kind? Did she have vouchers or discounts from previous visits? Did she load it all into plastic bags or, with a mind to the planet, carry with her canvas substitutes? I worry that she is not getting the best from her shopping sorties.

For example, does Mary not know about Ocado, and how you simply sit at your computer and order it all online – and then a van arrives at the time of your choosing and debouches everything you ordered on to your kitchen table, plus, by way of a "thank you" a packet of something you don't want but feel grateful to receive. Is she aware how you can tweak and twitch your order until the very last moment, how they will remind you what you bought last time, and suggest things that go well with, say, balsamic vinegar, stuffed vine leaves and body gel. I'd like to know whether she hires black London cabs or prefers a fleet of mini-cabs. And, if so, have the drivers got work permits or are they illegal immigrants? Once you start asking, you never know where you will end up. Except with people feeling guilty and shifty about the simple domestic matter of giving a dinner party, albeit in an official home that has just had a £1.3m makeover.

From the other direction of social lunacy, advance one Lord Snape, who came to Mary's rescue on Channel 4 News. In her defence, he declared: "Is the Speaker's wife supposed to queue for the No 12 bus when she does her shopping?" He said this expecting the outraged answer, "Certainly not – why humiliate the wretched woman?", whereas in fact many of us thought it was a no-brainer. Does Mary not know that if she is over 60 she can get a free bus pass, and that other passengers, struggling as they often are with pushchairs and such, are a friendly crowd who will help with those plastic (canvas?) bags and see her off at the numerous bus stops around Parliament Square.

As a teenager, I once saw Clement Attlee on a London Underground train. He was wearing a heavy Homberg hat, carrying a briefcase and quietly ignoring those around him – as they did him. He was prime minister at the time. Clearly, it was not beneath his dignity to travel with those who had elected him. Cannot the Speaker's wife, an attractive woman but hardly a face you'd readily recognise, still less someone to be harassed for their celebrity, travel along with the rest of us? OK, then. Take the bus or Tube to the supermarket, and get a taxi – loaded as she will be with balsamic vinegar and stuffed vine leaves – back to her official home. But what is humiliating about using the buses!

So who is this gallant Lord Snape who rushes to defend her? I expected to discover that he was one of the left-over hereditaries, tirelessly plodding on with outdated manners and surviving privileges. Not at all. He is none other than the former Labour MP for West Bromwich East, elevated to the upper house in 2004 – and a man who owned up in the 2007 debate about the Transport Bill to having been a consultant to the National Express Group, and a former director and chairman of its main bus subsidiary, Travel West Midlands. He actually had a hand in running buses – a mode of transport he now feels is too squalid to bear Mary Martin and her groceries.

All this is a long way from serious matter of state and government. It is the trivia of parliamentary gossip, and now an inquiry by the Parliamentary Standards Commissioner. But it is important trivia. The increasing gap between rich and poor – between the people and the grandees – is a factor of growing political significance. On every hand, we see the rich glutted with luxury and the poor wretched and depressed. Remember, It was Marie Antoinette's frivolous games as milkmaid – trivial but condescending – that fuelled the rising hatred of the rich. Well, it happened once!